Bacteriophages Facilitate the Survival of Lactic Acid Bacteria in Kimchi Fermentation

The World Institute of Kimchi (President: Hae Choon Chang), a government-funded research institute under the Ministry of Science and ICT, has confirmed in a new study that bacteriophages, which were previously considered a 'nuisance' during the process of food fermentation, actually play the role of key helpers that facilitate the survival of lactic acid bacteria (LAB).

Bacteriophages are viruses that infect bacteria. In the fermented food industry, they have long been considered the primary cause of fermentation delays or failure, as they interfere with the cultivation of LAB starters. However, the present research reversed our understanding by scientifically proving that bacteriophages are not simply viruses that kill bacteria, but rather are providers of genes that support the survival of LAB in a fermentation environment.

By using metagenomic and co-occurrence network analyses, metagenome and co-occurrence network analysis, the research team led by Dr. Tae-Woong Whon from the World Institute of Kimchi discovered that bacteriophages selectively infect specific types of LAB during the fermentation process, thereby helping other LAB to secure ecological space. In this way, bacteriophages contribute to maintaining the stability and diversity of LAB populations and play a role in controlling the LAB population balance. This is a kind of 'microbial traffic control' mechanism that mitigates competition among the LAB during the fermentation process, and this function of bacteriophages plays a key role in maintaining the unique flavor and consistent quality of kimchi.

It is particularly noteworthy that bacteriophages directly enhance the survivability of LAB in extreme fermentation environments. As fermentation progresses, environmental stress is intensified due to pH changes and the accumulation of metabolites. Bacteriophages transfer 'stress adaptation genes' to the LAB, thereby helping them to quickly adapt to the changing environment.

They also identified the six key genes, including genes associated with DnaB-like helicase essential for the stability of DNA replication, nicotinamide mononucleotide transporters crucial for optimizing energy metabolism, and deoxynucleoside kinase essential for DNA synthesis and repair, which enable the LAB to survive throughout the fermentation process, with the help of bacteriophages, thus ensuring the completion of fermentation.

This study not only provided a deeper scientific understanding of phage-host interactions in the fermentation ecosystem but also laid a scientific foundation for the development of microbial control strategies for the precise control of fermentation processes in the future.

Dr. Whon, who led this research, said, "We found that bacteriophages, which have long been regarded as problematic in the dairy industry due to starter culture infections, are actually hidden helpers in maintaining the balance of the fermentation ecosystem and improving the quality of kimchi."

The research results were published in LWT-Food Science and Technology (IF 6.6), a reputed international academic journal in the field of food science and technology.